Settings: Add get_flags API for mapgen flags (mg_flags, mgv6_spflags, ...) (#9284)

Unified flags handling in C++ and Lua Settings API
     -> Reading only, for now. Writing can be implemented later, if needed.
API function to read the currently active flags
     -> was impossible from Lua

Co-authored-by: Wuzzy <wuzzy2@mail.ru>

23 files changed, 222 insertions, 39 deletions

diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index 551aa50b5..1857ce541 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -6069,6 +6069,10 @@ It can be created via `Settings(filename)`.
     * `default` is the value returned if `key` is not found.
     * Returns `nil` if `key` is not found and `default` not specified.
 * `get_np_group(key)`: returns a NoiseParams table
+* `get_flags(key)`:
+    * Returns `{flag = true/false, ...}` according to the set flags.
+    * Is currently limited to mapgen flags `mg_flags` and mapgen-specific
+      flags like `mgv5_spflags`.
 * `set(key, value)`
     * Setting names can't contain whitespace or any of `="{}#`.
     * Setting values can't contain the sequence `\n"""`.
diff --git a/src/defaultsettings.cpp b/src/defaultsettings.cpp
index 1ab4a333e..754ce3547 100644
--- a/src/defaultsettings.cpp
+++ b/src/defaultsettings.cpp
@@ -24,6 +24,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "config.h"
 #include "constants.h"
 #include "porting.h"
+#include "mapgen/mapgen.h" // Mapgen::setDefaultSettings
 #include "util/string.h"
 
 void set_default_settings(Settings *settings)
@@ -426,10 +427,10 @@ void set_default_settings(Settings *settings)
 	settings->setDefault("water_level", "1");
 	settings->setDefault("mapgen_limit", "31000");
 	settings->setDefault("chunksize", "5");
-	settings->setDefault("mg_flags", "caves,dungeons,light,decorations,biomes");
 	settings->setDefault("fixed_map_seed", "");
 	settings->setDefault("max_block_generate_distance", "8");
 	settings->setDefault("enable_mapgen_debug_info", "false");
+	Mapgen::setDefaultSettings(settings);
 
 	// Server list announcing
 	settings->setDefault("server_announce", "false");
diff --git a/src/mapgen/mapgen.cpp b/src/mapgen/mapgen.cpp
index 81ccf1f8d..79c429ff6 100644
--- a/src/mapgen/mapgen.cpp
+++ b/src/mapgen/mapgen.cpp
@@ -215,6 +215,17 @@ void Mapgen::getMapgenNames(std::vector<const char *> *mgnames, bool include_hid
 	}
 }
 
+void Mapgen::setDefaultSettings(Settings *settings)
+{
+	settings->setDefault("mg_flags", flagdesc_mapgen,
+		 MG_CAVES | MG_DUNGEONS | MG_LIGHT | MG_DECORATIONS | MG_BIOMES);
+
+	for (int i = 0; i < (int)MAPGEN_INVALID; ++i) {
+		MapgenParams *params = createMapgenParams((MapgenType)i);
+		params->setDefaultSettings(settings);
+		delete params;
+	}
+}
 
 u32 Mapgen::getBlockSeed(v3s16 p, s32 seed)
 {
@@ -1068,7 +1079,7 @@ void MapgenParams::writeParams(Settings *settings) const
 	settings->setS16("water_level", water_level);
 	settings->setS16("mapgen_limit", mapgen_limit);
 	settings->setS16("chunksize", chunksize);
-	settings->setFlagStr("mg_flags", flags, flagdesc_mapgen, U32_MAX);
+	settings->setFlagStr("mg_flags", flags, flagdesc_mapgen);
 
 	if (bparams)
 		bparams->writeParams(settings);
diff --git a/src/mapgen/mapgen.h b/src/mapgen/mapgen.h
index 1473d41a6..dc325c791 100644
--- a/src/mapgen/mapgen.h
+++ b/src/mapgen/mapgen.h
@@ -124,7 +124,9 @@ struct MapgenParams {
 	u64 seed = 0;
 	s16 water_level = 1;
 	s16 mapgen_limit = MAX_MAP_GENERATION_LIMIT;
-	u32 flags = MG_CAVES | MG_LIGHT | MG_DECORATIONS | MG_BIOMES;
+	// Flags set in readParams
+	u32 flags = 0;
+	u32 spflags = 0;
 
 	BiomeParams *bparams = nullptr;
 
@@ -133,6 +135,8 @@ struct MapgenParams {
 
 	virtual void readParams(const Settings *settings);
 	virtual void writeParams(Settings *settings) const;
+	// Default settings for g_settings such as flags
+	virtual void setDefaultSettings(Settings *settings) {};
 
 	s32 getSpawnRangeMax();
 
@@ -214,6 +218,7 @@ public:
 		EmergeManager *emerge);
 	static MapgenParams *createMapgenParams(MapgenType mgtype);
 	static void getMapgenNames(std::vector<const char *> *mgnames, bool include_hidden);
+	static void setDefaultSettings(Settings *settings);
 
 private:
 	// isLiquidHorizontallyFlowable() is a helper function for updateLiquid()
diff --git a/src/mapgen/mapgen_carpathian.cpp b/src/mapgen/mapgen_carpathian.cpp
index 67f542c0d..0dc1d33be 100644
--- a/src/mapgen/mapgen_carpathian.cpp
+++ b/src/mapgen/mapgen_carpathian.cpp
@@ -187,7 +187,7 @@ void MapgenCarpathianParams::readParams(const Settings *settings)
 
 void MapgenCarpathianParams::writeParams(Settings *settings) const
 {
-	settings->setFlagStr("mgcarpathian_spflags", spflags, flagdesc_mapgen_carpathian, U32_MAX);
+	settings->setFlagStr("mgcarpathian_spflags", spflags, flagdesc_mapgen_carpathian);
 
 	settings->setFloat("mgcarpathian_base_level",   base_level);
 	settings->setFloat("mgcarpathian_river_width",  river_width);
@@ -227,6 +227,12 @@ void MapgenCarpathianParams::writeParams(Settings *settings) const
 }
 
 
+void MapgenCarpathianParams::setDefaultSettings(Settings *settings)
+{
+	settings->setDefault("mgcarpathian_spflags", flagdesc_mapgen_carpathian,
+		MGCARPATHIAN_CAVERNS);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 
diff --git a/src/mapgen/mapgen_carpathian.h b/src/mapgen/mapgen_carpathian.h
index ef49df213..acd379958 100644
--- a/src/mapgen/mapgen_carpathian.h
+++ b/src/mapgen/mapgen_carpathian.h
@@ -37,7 +37,6 @@ struct MapgenCarpathianParams : public MapgenParams
 	float river_depth      = 24.0f;
 	float valley_width     = 0.25f;
 
-	u32 spflags              = MGCARPATHIAN_CAVERNS;
 	float cave_width         = 0.09f;
 	s16 large_cave_depth     = -33;
 	u16 small_cave_num_min   = 0;
@@ -74,6 +73,7 @@ struct MapgenCarpathianParams : public MapgenParams
 
 	void readParams(const Settings *settings);
 	void writeParams(Settings *settings) const;
+	void setDefaultSettings(Settings *settings);
 };
 
 class MapgenCarpathian : public MapgenBasic
diff --git a/src/mapgen/mapgen_flat.cpp b/src/mapgen/mapgen_flat.cpp
index 656e7d72c..879435948 100644
--- a/src/mapgen/mapgen_flat.cpp
+++ b/src/mapgen/mapgen_flat.cpp
@@ -126,7 +126,7 @@ void MapgenFlatParams::readParams(const Settings *settings)
 
 void MapgenFlatParams::writeParams(Settings *settings) const
 {
-	settings->setFlagStr("mgflat_spflags", spflags, flagdesc_mapgen_flat, U32_MAX);
+	settings->setFlagStr("mgflat_spflags", spflags, flagdesc_mapgen_flat);
 	settings->setS16("mgflat_ground_level",         ground_level);
 	settings->setS16("mgflat_large_cave_depth",     large_cave_depth);
 	settings->setU16("mgflat_small_cave_num_min",   small_cave_num_min);
@@ -150,6 +150,12 @@ void MapgenFlatParams::writeParams(Settings *settings) const
 }
 
 
+void MapgenFlatParams::setDefaultSettings(Settings *settings)
+{
+	settings->setDefault("mgflat_spflags", flagdesc_mapgen_flat, 0);
+}
+
+
 /////////////////////////////////////////////////////////////////
 
 
diff --git a/src/mapgen/mapgen_flat.h b/src/mapgen/mapgen_flat.h
index 2ff87c0db..c314c7605 100644
--- a/src/mapgen/mapgen_flat.h
+++ b/src/mapgen/mapgen_flat.h
@@ -32,7 +32,6 @@ extern FlagDesc flagdesc_mapgen_flat[];
 
 struct MapgenFlatParams : public MapgenParams
 {
-	u32 spflags = 0;
 	s16 ground_level = 8;
 	s16 large_cave_depth = -33;
 	u16 small_cave_num_min = 0;
@@ -59,6 +58,7 @@ struct MapgenFlatParams : public MapgenParams
 
 	void readParams(const Settings *settings);
 	void writeParams(Settings *settings) const;
+	void setDefaultSettings(Settings *settings);
 };
 
 class MapgenFlat : public MapgenBasic
diff --git a/src/mapgen/mapgen_fractal.cpp b/src/mapgen/mapgen_fractal.cpp
index 1ac57cede..cabe0b850 100644
--- a/src/mapgen/mapgen_fractal.cpp
+++ b/src/mapgen/mapgen_fractal.cpp
@@ -139,7 +139,7 @@ void MapgenFractalParams::readParams(const Settings *settings)
 
 void MapgenFractalParams::writeParams(Settings *settings) const
 {
-	settings->setFlagStr("mgfractal_spflags", spflags, flagdesc_mapgen_fractal, U32_MAX);
+	settings->setFlagStr("mgfractal_spflags", spflags, flagdesc_mapgen_fractal);
 	settings->setFloat("mgfractal_cave_width",         cave_width);
 	settings->setS16("mgfractal_large_cave_depth",     large_cave_depth);
 	settings->setU16("mgfractal_small_cave_num_min",   small_cave_num_min);
@@ -167,6 +167,13 @@ void MapgenFractalParams::writeParams(Settings *settings) const
 }
 
 
+void MapgenFractalParams::setDefaultSettings(Settings *settings)
+{
+	settings->setDefault("mgfractal_spflags", flagdesc_mapgen_fractal,
+		MGFRACTAL_TERRAIN);
+}
+
+
 /////////////////////////////////////////////////////////////////
 
 
diff --git a/src/mapgen/mapgen_fractal.h b/src/mapgen/mapgen_fractal.h
index 0654d0360..971dfd822 100644
--- a/src/mapgen/mapgen_fractal.h
+++ b/src/mapgen/mapgen_fractal.h
@@ -35,7 +35,6 @@ extern FlagDesc flagdesc_mapgen_fractal[];
 
 struct MapgenFractalParams : public MapgenParams
 {
-	u32 spflags = MGFRACTAL_TERRAIN;
 	float cave_width = 0.09f;
 	s16 large_cave_depth = -33;
 	u16 small_cave_num_min = 0;
@@ -66,6 +65,7 @@ struct MapgenFractalParams : public MapgenParams
 
 	void readParams(const Settings *settings);
 	void writeParams(Settings *settings) const;
+	void setDefaultSettings(Settings *settings);
 };
 
 
diff --git a/src/mapgen/mapgen_v5.cpp b/src/mapgen/mapgen_v5.cpp
index c003c27d6..447fe8c50 100644
--- a/src/mapgen/mapgen_v5.cpp
+++ b/src/mapgen/mapgen_v5.cpp
@@ -129,7 +129,7 @@ void MapgenV5Params::readParams(const Settings *settings)
 
 void MapgenV5Params::writeParams(Settings *settings) const
 {
-	settings->setFlagStr("mgv5_spflags", spflags, flagdesc_mapgen_v5, U32_MAX);
+	settings->setFlagStr("mgv5_spflags", spflags, flagdesc_mapgen_v5);
 	settings->setFloat("mgv5_cave_width",         cave_width);
 	settings->setS16("mgv5_large_cave_depth",     large_cave_depth);
 	settings->setU16("mgv5_small_cave_num_min",   small_cave_num_min);
@@ -154,6 +154,15 @@ void MapgenV5Params::writeParams(Settings *settings) const
 }
 
 
+void MapgenV5Params::setDefaultSettings(Settings *settings)
+{
+	settings->setDefault("mgv5_spflags", flagdesc_mapgen_v5, MGV5_CAVERNS);
+}
+
+
+/////////////////////////////////////////////////////////////////
+
+
 int MapgenV5::getSpawnLevelAtPoint(v2s16 p)
 {
 
diff --git a/src/mapgen/mapgen_v5.h b/src/mapgen/mapgen_v5.h
index ecdcdaf41..17bc466f0 100644
--- a/src/mapgen/mapgen_v5.h
+++ b/src/mapgen/mapgen_v5.h
@@ -31,7 +31,6 @@ extern FlagDesc flagdesc_mapgen_v5[];
 
 struct MapgenV5Params : public MapgenParams
 {
-	u32 spflags = MGV5_CAVERNS;
 	float cave_width = 0.09f;
 	s16 large_cave_depth = -256;
 	u16 small_cave_num_min = 0;
@@ -59,6 +58,7 @@ struct MapgenV5Params : public MapgenParams
 
 	void readParams(const Settings *settings);
 	void writeParams(Settings *settings) const;
+	void setDefaultSettings(Settings *settings);
 };
 
 class MapgenV5 : public MapgenBasic
diff --git a/src/mapgen/mapgen_v6.cpp b/src/mapgen/mapgen_v6.cpp
index 4e876fc53..653adc8ec 100644
--- a/src/mapgen/mapgen_v6.cpp
+++ b/src/mapgen/mapgen_v6.cpp
@@ -190,7 +190,7 @@ void MapgenV6Params::readParams(const Settings *settings)
 
 void MapgenV6Params::writeParams(Settings *settings) const
 {
-	settings->setFlagStr("mgv6_spflags", spflags, flagdesc_mapgen_v6, U32_MAX);
+	settings->setFlagStr("mgv6_spflags", spflags, flagdesc_mapgen_v6);
 	settings->setFloat("mgv6_freq_desert", freq_desert);
 	settings->setFloat("mgv6_freq_beach",  freq_beach);
 	settings->setS16("mgv6_dungeon_ymin",  dungeon_ymin);
@@ -210,8 +210,16 @@ void MapgenV6Params::writeParams(Settings *settings) const
 }
 
 
+void MapgenV6Params::setDefaultSettings(Settings *settings)
+{
+	settings->setDefault("mgv6_spflags", flagdesc_mapgen_v6, MGV6_JUNGLES |
+		MGV6_SNOWBIOMES | MGV6_TREES | MGV6_BIOMEBLEND | MGV6_MUDFLOW);
+}
+
+
 //////////////////////// Some helper functions for the map generator
 
+
 // Returns Y one under area minimum if not found
 s16 MapgenV6::find_stone_level(v2s16 p2d)
 {
diff --git a/src/mapgen/mapgen_v6.h b/src/mapgen/mapgen_v6.h
index 7d5229559..d8cdcb26f 100644
--- a/src/mapgen/mapgen_v6.h
+++ b/src/mapgen/mapgen_v6.h
@@ -55,8 +55,6 @@ enum BiomeV6Type
 
 
 struct MapgenV6Params : public MapgenParams {
-	u32 spflags = MGV6_JUNGLES | MGV6_SNOWBIOMES | MGV6_TREES |
-		MGV6_BIOMEBLEND | MGV6_MUDFLOW;
 	float freq_desert = 0.45f;
 	float freq_beach = 0.15f;
 	s16 dungeon_ymin = -31000;
@@ -79,6 +77,7 @@ struct MapgenV6Params : public MapgenParams {
 
 	void readParams(const Settings *settings);
 	void writeParams(Settings *settings) const;
+	void setDefaultSettings(Settings *settings);
 };
 
 
diff --git a/src/mapgen/mapgen_v7.cpp b/src/mapgen/mapgen_v7.cpp
index 23cbd4e0a..325c4957a 100644
--- a/src/mapgen/mapgen_v7.cpp
+++ b/src/mapgen/mapgen_v7.cpp
@@ -183,7 +183,7 @@ void MapgenV7Params::readParams(const Settings *settings)
 
 void MapgenV7Params::writeParams(Settings *settings) const
 {
-	settings->setFlagStr("mgv7_spflags", spflags, flagdesc_mapgen_v7, U32_MAX);
+	settings->setFlagStr("mgv7_spflags", spflags, flagdesc_mapgen_v7);
 	settings->setS16("mgv7_mount_zero_level",           mount_zero_level);
 	settings->setFloat("mgv7_cave_width",               cave_width);
 	settings->setS16("mgv7_large_cave_depth",           large_cave_depth);
@@ -214,6 +214,13 @@ void MapgenV7Params::writeParams(Settings *settings) const
 }
 
 
+void MapgenV7Params::setDefaultSettings(Settings *settings)
+{
+	settings->setDefault("mgv7_spflags", flagdesc_mapgen_v7,
+		MGV7_MOUNTAINS | MGV7_RIDGES | MGV7_CAVERNS);
+}
+
+
 ////////////////////////////////////////////////////////////////////////////////
 
 
diff --git a/src/mapgen/mapgen_v7.h b/src/mapgen/mapgen_v7.h
index 6ca39f164..0605c5c97 100644
--- a/src/mapgen/mapgen_v7.h
+++ b/src/mapgen/mapgen_v7.h
@@ -35,7 +35,6 @@ extern FlagDesc flagdesc_mapgen_v7[];
 
 
 struct MapgenV7Params : public MapgenParams {
-	u32 spflags = MGV7_MOUNTAINS | MGV7_RIDGES | MGV7_CAVERNS;
 	s16 mount_zero_level = 0;
 
 	float cave_width = 0.09f;
@@ -70,6 +69,7 @@ struct MapgenV7Params : public MapgenParams {
 
 	void readParams(const Settings *settings);
 	void writeParams(Settings *settings) const;
+	void setDefaultSettings(Settings *settings);
 };
 
 
diff --git a/src/mapgen/mapgen_valleys.cpp b/src/mapgen/mapgen_valleys.cpp
index 3c6045105..2b8703fa5 100644
--- a/src/mapgen/mapgen_valleys.cpp
+++ b/src/mapgen/mapgen_valleys.cpp
@@ -162,7 +162,7 @@ void MapgenValleysParams::readParams(const Settings *settings)
 
 void MapgenValleysParams::writeParams(Settings *settings) const
 {
-	settings->setFlagStr("mgvalleys_spflags", spflags, flagdesc_mapgen_valleys, U32_MAX);
+	settings->setFlagStr("mgvalleys_spflags", spflags, flagdesc_mapgen_valleys);
 	settings->setU16("mgvalleys_altitude_chill",       altitude_chill);
 	settings->setS16("mgvalleys_large_cave_depth",     large_cave_depth);
 	settings->setU16("mgvalleys_small_cave_num_min",   small_cave_num_min);
@@ -194,6 +194,17 @@ void MapgenValleysParams::writeParams(Settings *settings) const
 }
 
 
+void MapgenValleysParams::setDefaultSettings(Settings *settings)
+{
+	settings->setDefault("mgvalleys_spflags", flagdesc_mapgen_valleys,
+		MGVALLEYS_ALT_CHILL | MGVALLEYS_HUMID_RIVERS |
+		MGVALLEYS_VARY_RIVER_DEPTH | MGVALLEYS_ALT_DRY);
+}
+
+
+/////////////////////////////////////////////////////////////////
+
+
 void MapgenValleys::makeChunk(BlockMakeData *data)
 {
 	// Pre-conditions
diff --git a/src/mapgen/mapgen_valleys.h b/src/mapgen/mapgen_valleys.h
index be97f0763..1aec68842 100644
--- a/src/mapgen/mapgen_valleys.h
+++ b/src/mapgen/mapgen_valleys.h
@@ -41,8 +41,6 @@ extern FlagDesc flagdesc_mapgen_valleys[];
 
 
 struct MapgenValleysParams : public MapgenParams {
-	u32 spflags = MGVALLEYS_ALT_CHILL | MGVALLEYS_HUMID_RIVERS |
-		MGVALLEYS_VARY_RIVER_DEPTH | MGVALLEYS_ALT_DRY;
 	u16 altitude_chill = 90;
 	u16 river_depth = 4;
 	u16 river_size = 5;
@@ -78,6 +76,7 @@ struct MapgenValleysParams : public MapgenParams {
 
 	void readParams(const Settings *settings);
 	void writeParams(Settings *settings) const;
+	void setDefaultSettings(Settings *settings);
 };
 
 
diff --git a/src/script/lua_api/l_settings.cpp b/src/script/lua_api/l_settings.cpp
index cc2c73789..33eb02392 100644
--- a/src/script/lua_api/l_settings.cpp
+++ b/src/script/lua_api/l_settings.cpp
@@ -20,6 +20,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "lua_api/l_settings.h"
 #include "lua_api/l_internal.h"
 #include "cpp_api/s_security.h"
+#include "util/string.h" // FlagDesc
 #include "settings.h"
 #include "noise.h"
 #include "log.h"
@@ -128,6 +129,29 @@ int LuaSettings::l_get_np_group(lua_State *L)
 	return 1;
 }
 
+int LuaSettings::l_get_flags(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+	LuaSettings *o = checkobject(L, 1);
+	std::string key = std::string(luaL_checkstring(L, 2));
+
+	u32 flags = 0;
+	auto flagdesc = o->m_settings->getFlagDescFallback(key);
+	if (o->m_settings->getFlagStrNoEx(key, flags, flagdesc)) {
+		lua_newtable(L);
+		int table = lua_gettop(L);
+		for (size_t i = 0; flagdesc[i].name; ++i) {
+			lua_pushboolean(L, flags & flagdesc[i].flag);
+			lua_setfield(L, table, flagdesc[i].name);
+		}
+		lua_pushvalue(L, table);
+	} else {
+		lua_pushnil(L);
+	}
+
+	return 1;
+}
+
 // set(self, key, value)
 int LuaSettings::l_set(lua_State* L)
 {
@@ -305,6 +329,7 @@ const luaL_Reg LuaSettings::methods[] = {
 	luamethod(LuaSettings, get),
 	luamethod(LuaSettings, get_bool),
 	luamethod(LuaSettings, get_np_group),
+	luamethod(LuaSettings, get_flags),
 	luamethod(LuaSettings, set),
 	luamethod(LuaSettings, set_bool),
 	luamethod(LuaSettings, set_np_group),
diff --git a/src/script/lua_api/l_settings.h b/src/script/lua_api/l_settings.h
index dcf39a89e..67d7b342b 100644
--- a/src/script/lua_api/l_settings.h
+++ b/src/script/lua_api/l_settings.h
@@ -42,6 +42,9 @@ private:
 	// get_np_group(self, key) -> noiseparam
 	static int l_get_np_group(lua_State *L);
 
+	// get_flags(self, key) -> key/value table
+	static int l_get_flags(lua_State *L);
+
 	// set(self, key, value)
 	static int l_set(lua_State *L);
 
diff --git a/src/settings.cpp b/src/settings.cpp
index c1fe41fa3..3728fabf2 100644
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -484,12 +484,33 @@ v3f Settings::getV3F(const std::string &name) const
 u32 Settings::getFlagStr(const std::string &name, const FlagDesc *flagdesc,
 	u32 *flagmask) const
 {
-	std::string val = get(name);
-	return std::isdigit(val[0])
-		? stoi(val)
-		: readFlagString(val, flagdesc, flagmask);
-}
+	u32 flags = 0;
+	u32 mask_default = 0;
+
+	std::string value;
+	// Read default value (if there is any)
+	if (getDefaultNoEx(name, value)) {
+		flags = std::isdigit(value[0])
+			? stoi(value)
+			: readFlagString(value, flagdesc, &mask_default);
+	}
+
+	// Apply custom flags "on top"
+	value = get(name);
+	u32 flags_user;
+	u32 mask_user = U32_MAX;
+	flags_user = std::isdigit(value[0])
+		? stoi(value) // Override default
+		: readFlagString(value, flagdesc, &mask_user);
 
+	flags &= ~mask_user;
+	flags |=  flags_user;
+
+	if (flagmask)
+		*flagmask = mask_default | mask_user;
+
+	return flags;
+}
 
 // N.B. if getStruct() is used to read a non-POD aggregate type,
 // the behavior is undefined.
@@ -736,19 +757,16 @@ bool Settings::getV3FNoEx(const std::string &name, v3f &val) const
 }
 
 
-// N.B. getFlagStrNoEx() does not set val, but merely modifies it.  Thus,
-// val must be initialized before using getFlagStrNoEx().  The intention of
-// this is to simplify modifying a flags field from a default value.
 bool Settings::getFlagStrNoEx(const std::string &name, u32 &val,
-	FlagDesc *flagdesc) const
+	const FlagDesc *flagdesc) const
 {
-	try {
-		u32 flags, flagmask;
-
-		flags = getFlagStr(name, flagdesc, &flagmask);
+	if (!flagdesc) {
+		if (!(flagdesc = getFlagDescFallback(name)))
+			return false; // Not found
+	}
 
-		val &= ~flagmask;
-		val |=  flags;
+	try {
+		val = getFlagStr(name, flagdesc, nullptr);
 
 		return true;
 	} catch (SettingNotFoundException &e) {
@@ -873,6 +891,11 @@ bool Settings::setV3F(const std::string &name, v3f value)
 bool Settings::setFlagStr(const std::string &name, u32 flags,
 	const FlagDesc *flagdesc, u32 flagmask)
 {
+	if (!flagdesc) {
+		if (!(flagdesc = getFlagDescFallback(name)))
+			return false; // Not found
+	}
+
 	return set(name, writeFlagString(flags, flagdesc, flagmask));
 }
 
@@ -1018,6 +1041,18 @@ void Settings::clearDefaultsNoLock()
 	m_defaults.clear();
 }
 
+void Settings::setDefault(const std::string &name, const FlagDesc *flagdesc,
+	u32 flags)
+{
+	m_flags[name] = flagdesc;
+	setDefault(name, writeFlagString(flags, flagdesc, U32_MAX));
+}
+
+const FlagDesc *Settings::getFlagDescFallback(const std::string &name) const
+{
+	auto it = m_flags.find(name);
+	return it == m_flags.end() ? nullptr : it->second;
+}
 
 void Settings::registerChangedCallback(const std::string &name,
 	SettingsChangedCallback cbf, void *userdata)
diff --git a/src/settings.h b/src/settings.h
index 329a61140..b42e36d10 100644
--- a/src/settings.h
+++ b/src/settings.h
@@ -174,10 +174,12 @@ public:
 	bool getFloatNoEx(const std::string &name, float &val) const;
 	bool getV2FNoEx(const std::string &name, v2f &val) const;
 	bool getV3FNoEx(const std::string &name, v3f &val) const;
-	// N.B. getFlagStrNoEx() does not set val, but merely modifies it.  Thus,
-	// val must be initialized before using getFlagStrNoEx().  The intention of
-	// this is to simplify modifying a flags field from a default value.
-	bool getFlagStrNoEx(const std::string &name, u32 &val, FlagDesc *flagdesc) const;
+
+	// Like other getters, but handling each flag individualy:
+	// 1) Read default flags (or 0)
+	// 2) Override using user-defined flags
+	bool getFlagStrNoEx(const std::string &name, u32 &val,
+		const FlagDesc *flagdesc) const;
 
 
 	/***********
@@ -201,7 +203,7 @@ public:
 	bool setV2F(const std::string &name, v2f value);
 	bool setV3F(const std::string &name, v3f value);
 	bool setFlagStr(const std::string &name, u32 flags,
-		const FlagDesc *flagdesc, u32 flagmask);
+		const FlagDesc *flagdesc = nullptr, u32 flagmask = U32_MAX);
 	bool setNoiseParams(const std::string &name, const NoiseParams &np,
 		bool set_default=false);
 	// N.B. if setStruct() is used to write a non-POD aggregate type,
@@ -215,6 +217,13 @@ public:
 	void updateValue(const Settings &other, const std::string &name);
 	void update(const Settings &other);
 
+	/**************
+	 * Miscellany *
+	 **************/
+
+	void setDefault(const std::string &name, const FlagDesc *flagdesc, u32 flags);
+	const FlagDesc *getFlagDescFallback(const std::string &name) const;
+
 	void registerChangedCallback(const std::string &name,
 		SettingsChangedCallback cbf, void *userdata = NULL);
 	void deregisterChangedCallback(const std::string &name,
@@ -229,6 +238,7 @@ private:
 
 	SettingEntries m_settings;
 	SettingEntries m_defaults;
+	std::unordered_map<std::string, const FlagDesc *> m_flags;
 
 	SettingsCallbackMap m_callbacks;
 
diff --git a/src/unittest/test_settings.cpp b/src/unittest/test_settings.cpp
index b2666559e..aa56f3e06 100644
--- a/src/unittest/test_settings.cpp
+++ b/src/unittest/test_settings.cpp
@@ -31,6 +31,7 @@ public:
 	void runTests(IGameDef *gamedef);
 
 	void testAllSettings();
+	void testFlagDesc();
 
 	static const char *config_text_before;
 	static const std::string config_text_after;
@@ -41,6 +42,7 @@ static TestSettings g_test_instance;
 void TestSettings::runTests(IGameDef *gamedef)
 {
 	TEST(testAllSettings);
+	TEST(testFlagDesc);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -206,3 +208,38 @@ void TestSettings::testAllSettings()
 		UASSERT(!"Setting not found!");
 	}
 }
+
+void TestSettings::testFlagDesc()
+{
+	Settings s;
+	FlagDesc flagdesc[] = {
+		{ "biomes",  0x01 },
+		{ "trees",   0x02 },
+		{ "jungles", 0x04 },
+		{ "oranges", 0x08 },
+		{ "tables",  0x10 },
+		{ nullptr,      0 }
+	};
+
+	// Enabled: biomes, jungles, oranges (default)
+	s.setDefault("test_desc", flagdesc, readFlagString(
+		"biomes,notrees,jungles,oranges", flagdesc, nullptr));
+	UASSERT(s.getFlagStr("test_desc", flagdesc, nullptr) == (0x01 | 0x04 | 0x08));
+
+	// Enabled: jungles, oranges, tables
+	s.set("test_desc", "nobiomes,tables");
+	UASSERT(s.getFlagStr("test_desc", flagdesc, nullptr) == (0x04 | 0x08 | 0x10));
+
+	// Enabled: (nothing)
+	s.set("test_desc", "nobiomes,nojungles,nooranges,notables");
+	UASSERT(s.getFlagStr("test_desc", flagdesc, nullptr) == 0x00);
+
+	// Numeric flag tests (override)
+	// Enabled: trees, tables
+	s.setDefault("test_flags", flagdesc, 0x02 | 0x10);
+	UASSERT(s.getFlagStr("test_flags", flagdesc, nullptr) == (0x02 | 0x10));
+
+	// Enabled: tables
+	s.set("test_flags", "16");
+	UASSERT(s.getFlagStr("test_flags", flagdesc, nullptr) == 0x10);
+}